Packaging articles suitable for scavenging oxygen

ABSTRACT

An article useful for packaging oxygen-sensitive products is disclosed. The article is a single or multi-layer article capable of enveloping the oxygen sensitive product. The article has at least one layer which contains a composition composed of an ethylenically unsaturated hydrocarbon polymer and a transition metal salt. The layer is capable of scavenging oxygen at a rate of at least 1 cc oxygen per square meter per day and has a capacity of at least 250 cc oxygen per square meter per mil thickness of the layer.

This is a continuation of application Ser. No. 08/268,047, filed Jun.28, 1994, now abandoned which is a division, of application Ser. No.052,851, filed Apr. 23, 1993, now U.S. Pat. No. 5,346,644 which is acontinuation-in-part of our application U.S. Ser. No. 679,419 filed Apr.2, 1991 now abandoned for "Compositions, Articles and Methods forScavenging Oxygen", incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention generally relates to compositions, articles and methodsfor scavenging oxygen in environments containing oxygen-sensitiveproducts, particularly food and beverage products. As will be evidentfrom the disclosure below, the term "oxygen scavenger" refers tocompositions, articles or the like which consume, deplete or reduce theamount of oxygen from a given environment.

BACKGROUND OF THE INVENTION

It is well known that regulating the exposure of oxygen-sensitiveproducts to oxygen maintains and enhances the quality and "shelf-life"of the product. For instance, by limiting the oxygen exposure of oxygensensitive food products in a packaging system, the quality of the foodproduct is maintained, and food spoilage is avoided. In addition suchpackaging also keeps the product in inventory longer, thereby reducingcosts incurred from waste and having to restock inventory. In the foodpackaging industry, several means for regulating oxygen exposure havealready been developed. These means include modified atmospherepackaging (MAP) and oxygen barrier film packaging.

One method currently being used is through "active packaging," wherebythe package for the food product is modified in some manner to regulatethe food product's exposure to oxygen. See Labuza and Breene,"Application of `Active Packaging` for Improvement of Shelf Life andNutritional Quality of Fresh and Extended Shelf-Life Foods," Journal ofFood Processing and Preservation, Vol. 13, pp. 1-69 (1989). Theinclusion of oxygen scavengers within the cavity of the package is oneform of active packaging. Typically, such oxygen scavengers are in theform of sachets which contain a composition which scavenges the oxygenthrough oxidation reactions. One sachet contains iron-based compositionswhich oxidize to their ferric states. Another type of sachet containsunsaturated fatty acid salts on a particulate adsorbent. See U.S. Pat.No. 4,908,151. Yet another sachet contains metal/polyamide complex. SeePCT Application 90/00578.

However, one disadvantage of sachets is the need for additionalpackaging operations to add the sachet to each package. A furtherdisadvantage arising from the iron-based sachets is that certainatmospheric conditions (e.g., high humidity, low CO₂ level) in thepackage are sometimes required in order for scavenging to occur at anadequate rate.

Another means for regulating the exposure to oxygen involvesincorporating an oxygen scavenger into the packaging structure itself.Through the incorporation of the scavenging material in the packageitself rather than by addition of a separate scavenger structure (e.g.,a sachet) to the package, a more uniform scavenging effect throughoutthe package is achieved. This may be especially important where there isrestricted air flow inside the package. In addition, such incorporationcan provide a means of intercepting and scavenging oxygen as it ispassing through the walls of the package (herein referred to as an"active oxygen barrier"), thereby maintaining the lowest possible oxygenlevel throughout the package.

One attempt to prepare an oxygen-scavenging wall involves theincorporation of inorganic powders and/or salts. See EuropeanApplications 367,835; 366,254; 367,390; and 370,802. However,incorporation of these powders and/or salts causes degradation of thewall's transparency and mechanical properties such as tear strength. Inaddition, these compounds can lead to processing difficulties,especially in the fabrication of thin layers such as thin films. Evenfurther, the scavenging rates for walls containing these compoundsappear to be unsuitable for many commercial oxygen-scavengingapplications, e.g. such as those in which sachets are employed.

The oxygen scavenging systems disclosed in European Applications 301,719and 380,319 as well as disclosed in PCT 90/00578 and 90/00504 illustrateanother attempt to produce an oxygen-scavenging wall. These patentapplications disclose incorporating a metal catalyst-polyamide oxygenscavenging system into the package wall. Through the catalyzed oxidationof the polyamide, the package wall regulates the amount of oxygen whichreaches the cavity of the package (active oxygen barrier) and has beenreported to have oxygen scavenging rate capabilities up to about 5 cubiccentimeters (cc) oxygen per square meter per day at ambient conditions.However, this system does suffer from significant disadvantages.

One particularly limiting disadvantage of the polyamide/catalystmaterials is its rate of oxygen scavenging. European Application 301,719(Example 7) illustrates that adding these materials to a high-barrierpackage containing air produces a package which is not generallysuitable for creating an internal oxygen level of less than 0.1%(starting with air) within a period of four weeks or less at roomtemperature, as is typically required for headspace oxygen scavengingapplications. See Mitsubishi Gas Chemical Company, Inc.'s literaturetitled "AGELESS®--A New Age in Food Preservation" (date unknown).

Further, in regards to the incorporation of the polyamide/catalystsystem into the package wall, polyamides are typically incompatible withthe thermoplastic polymers, e.g. ethylene-vinyl acetate copolymers andlow density polyethylenes, typically used to make flexible packagewalls. Even further, when polyamides are used by themselves to make aflexible package wall, they may result in inappropriately stiffstructures. Polyamides also incur processing difficulties and highercosts when compared with the costs of thermoplastic polymers typicallyused to make flexible packaging. Even further, they are sometimesdifficult to heat seal. Thus, all of these are factors to consider whenselecting materials for packages, especially flexible packages and whenselecting systems for reducing oxygen exposure of packaged products.

SUMMARY OF THE INVENTION

It is an object of the invention to obtain a composition which iseffective as an oxygen scavenger and is suitable for incorporating intolayers used in articles containing oxygen-sensitive products.

It is a further object to obtain an oxygen scavenging composition whichis compatible with the materials typically used to prepare such layers.

It is also an object to obtain compositions for scavenging oxygen whichcan be used in a flexible layer in a multilayer article containingoxygen-sensitive products.

It is a further object of the invention to provide a novel compositionsuitable for use in packaging of food and beverage products.

It is thus an even further overall object of the invention to overcomethe above-mentioned disadvantages of previously used oxygen-scavengingmethods.

The above-mentioned objects are obtained from a novel compositioncomprising:

(a) an ethylenically unsaturated hydrocarbon and

(b) a transition metal catalyst.

When the composition is incorporated into a layer such as a film layer,novel articles for packaging oxygen-sensitive products can be preparedtherefrom and thus provide a new method for limiting the exposure ofsuch products to oxygen. The articles used in those methods limit theoxygen exposure by acting as an active oxygen barrier and/or acting asmeans for scavenging oxygen from within the article.

The above-mentioned goals and others will be apparent from thedescription that follows.

DESCRIPTION OF THE INVENTION

The invention can be used in packaging articles having several forms.Suitable articles include, but are not limited to, rigid containers,flexible bags, or combinations of both. Typical rigid or semi-rigidarticles include plastic, paper or cardboard cartons or bottles such asjuice containers, soft drink containers, thermoformed trays or cupswhich have wall thicknesses in the range of 100 to 1000 micrometers.Typical flexible bags include those used to package many food items, andwill likely have thicknesses of 5 to 250 micrometers. In addition thewalls of such articles often comprise multiple layers of material. Thisinvention can be used in one, some or all of those layers.

Though it may be preferable from the standpoint of packaging convenienceand/or scavenging effectiveness to employ the invention as an integralpart of the package wall, the invention can also be used as anon-integral packaging component, e.g. coatings, bottle cap liners,adhesive or non-adhesive sheet inserts, sealants or fibrous mat inserts.

Besides packaging articles for food and beverage, packaging for otheroxygen-sensitive products can benefit from the invention. Such productswould be pharmaceuticals, oxygen sensitive medical products, corrodiblemetals or products such as electronic devices, etc.

The ethylenically unsaturated hydrocarbon (a) may be either substitutedor unsubstituted. As defined herein, an unsubstituted ethylenicallyunsaturated hydrocarbon is any compound which possesses at least onealiphatic carbon-carbon double bond and comprises 100% by weight carbonand hydrogen. A substituted ethylenically unsaturated hydrocarbon isdefined herein as an ethylenically unsaturated hydrocarbon whichpossesses at least one aliphatic carbon-carbon double bond and comprisesabout 50%-99% by weight carbon and hydrogen. Preferable substituted orunsubstituted ethylenically unsaturated hydrocarbons are those havingtwo or more ethylenically unsaturated groups per molecule. Morepreferably, it is a polymeric compound having three or moreethylenically unsaturated groups and a molecular weight equal to orgreater than 1,000 weight average molecular weight.

Preferred examples of unsubstituted ethylenically unsaturatedhydrocarbons include, but are not limited to, diene polymers such aspolyisoprene, (e.g., trans-polyisoprene), polybutadiene (especially1,2-polybutadienes, which are defined as those polybutadienes possessinggreater than or equal to 50% 1,2 microstructure), and copolymersthereof, e.g. styrene-butadiene. Such hydrocarbons also includepolymeric compounds such as polypentenamer, polyoctenamer, and otherpolymers prepared by olefin metathesis; diene oligomers such assqualene; and polymers or copolymers derived from dicyclopentadiene,norbornadiene, 5-ethylidene-2-norbornene, or other monomers containingmore than one carbon-carbon double bond (conjugated or non-conjugated).These hydro-carbons further include carotenoids such as β-carotene.

Preferred substituted ethylenically unsaturated hydrocarbons include,but are not limited to, those with oxygen-containing moieties, such asesters, carboxylic acids, aldehydes, ethers, ketones, alcohols,peroxides, and/or hydroperoxides. Specific examples of such hydrocarbonsinclude, but are not limited to, condensation polymers such aspolyesters derived from monomers containing carbon-carbon double bonds;unsaturated fatty acids such as oleic, ricinoleic, dehydratedricinoleic, and linoleic acids and derivatives thereof, e.g. esters.Such hydrocarbons also include polymers or copolymers derived from(meth)allyl (meth)acrylates.

The composition used may also comprise a mixture of two or more of thesubstituted or unsubstituted ethylenically unsaturated hydrocarbonsdescribed above.

As will also be evident, ethylenically unsaturated hydrocarbons whichare appropriate for forming solid transparent layers at room temperatureare preferred for scavenging oxygen in the packaging articles describedabove. For most applications where transparency is necessary, a layerwhich allows at least 50% transmission of visible light is acceptable.

When making transparent oxygen-scavenging layers according to thisinvention, 1,2-polybutadiene is especially preferred as component (a).For instance, 1,2-polybutadiene can exhibit transparency, mechanicalproperties and processing characteristics similar to those ofpolyethylene. In addition, this polymer is found to retain itstransparency and mechanical integrity even after most or all of itsoxygen capacity has been consumed, and even when little or no diluentresin is present. Even further, 1,2-polybutadiene exhibits a relativelyhigh oxygen capacity and, once it has begun to scavenge, it exhibits arelatively high scavenging rate as well.

As indicated above, (b) is a transition metal catalyst. While not beingbound by any particular theory, suitable metal catalysts are those whichcan readily interconvert between at least two oxidation states. SeeSheldon, R. A.; Kochi, J. K.; "Metal-Catalyzed Oxidations of OrganicCompounds" Academic Press, New York 1981.

Preferably, (b) is in the form of a transition metal salt, with themetal selected from the first, second or third transition series of thePeriodic Table. Suitable metals include, but are not limited to,manganese II or III, iron II or III, cobalt II or III, nickel II or III,copper I or II, rhodium II, III or IV, and ruthenium. The oxidationstate of the metal when introduced is not necessarily that of the activeform. The metal is preferably iron, nickel or copper, more preferablymanganese and most preferably cobalt. Suitable counterions for the metalinclude, but are not limited to, chloride, acetate, stearate, palmitate,2-ethylhexanoate, neodecanoate or naphthenate. Particularly preferablesalts include cobalt (II) 2-ethylhexanoate and cobalt (II) neodecanoate.The metal salt may also be an ionomer, in which case a polymericcounterion is employed. Such ionomers are well known in the art.

When making layers, such as film layers, from compositions wherein (a)is a polymeric compound such as polybutadiene, polyisoprene orcopolymers thereof or polypentenamer, etc., the layer can be prepareddirectly from (a). On the other hand, (a) and transition metal catalyst(b) may be further combined with one or more polymeric diluents, such asthermoplastic polymers which are typically used to form film layers inplastic packaging articles. Even in the event (a) is a thermoplasticpolymer, e.g. polybutadiene, it is sometimes suitable to include one ormore additional polymeric diluents. In the manufacture of certainpackaging articles well known thermosets can also be used as thepolymeric diluent.

Selecting combinations of diluent and (a) depends on the propertiesdesired. Polymers which can be used as the diluent include, but are notlimited to, polyethylene terephthalate (PET), polyethylene, low or verylow density polyethylene, ultra-low density polyethylene, linear lowdensity polyethylene, polypropylene, polyvinyl chloride, polystyrene,and ethylene copolymers such as ethylene-vinyl acetate, ethylene-alkyl(meth)acrylates, ethylene-(meth)acrylic acid and ethylene-(meth)acrylicacid ionomers. In rigid articles such as beverage containers PET isoften used. See European Application 301,719. Blends of differentdiluents may also be used. However, as indicated above, the selection ofthe polymeric diluent largely depends on the article to be manufacturedand the end use. Such selection factors are well known in the art.

If a diluent polymer-such as a thermoplastic is employed, it shouldfurther be selected according to its compatibility with theethylenically unsaturated hydrocarbon selected for (a). In someinstances, the clarity, cleanliness, effectiveness as an oxygenscavenger, barrier properties, mechanical properties and/or texture ofthe article can be adversely affected by a blend containing a polymerwhich is incompatible with (a). For instance, it has been found thatwhen (a) is dehydrated castor oil, a less "greasy" film is prepared froma blend with ethylene-acrylic acid copolymer than with ethylene vinylacetate copolymer.

Further additives may also be included in the composition to impartproperties desired for the particular article being manufactured. Suchadditives include, but are not necessarily limited to, fillers,pigments, dyestuffs, antioxidants, stabilizers, processing aids,plasticizers, fire retardants, anti-fog agents, etc.

The mixing of the components listed above is preferably accomplished bymelt-blending at a temperature in the range of 50° C. to 300° C. Howeveralternatives such as the use of a solvent followed by evaporation mayalso be employed. The blending may immediately precede the formation ofthe finished article or preform or precede the formation of a feedstockor masterbatch for later use in the production of finished packagingarticles. When making film layers or articles from oxygen-scavengingcompositions, (co)extrusion, solvent casting, injection molding, stretchblow molding, orientation, thermoforming, extrusion coating, coating andcuring, lamination or combinations thereof would typically follow theblending.

The amounts of (a), (b), optional polymeric diluents and additives, varydepending on the article to be manufactured and its end use. Theseamounts also depend on the desired oxygen scavenging capacity, thedesired oxygen scavenging rate, and the particular materials selected.

For instance, the primary function of (a) is to react irreversibly withoxygen during the scavenging process, and the primary function of (b) isto facilitate this process. Thus, to a large extent, the amount of (a)will affect the oxygen capacity of the composition, i.e., affect theamount of oxygen that the composition can consume, and the amount of (b)will affect the rate at which oxygen is consumed. It also thus followsthat the amount of (a) is selected in accordance with the scavengingcapacity needed for a particular application, and the amount of (b) isselected in accordance with the scavenging rate needed. Typically, theamount of (a) may range from 1 to 99%, preferably from 10 to 99%, byweight of the composition or layer in which both (a) and (b) are present(herein referred to as the "scavenging component", e.g., in a coextrudedfilm, the scavenging component would comprise the particular layer(s) inwhich (a) and (b) are present together). Typically, the amount of (b)may range from 0.001 to 1% (10 to 10,000 ppm) of the scavengingcomponent, based on the metal content only (excluding ligands,counterions, etc.). In the event the amount of (b) is about 0.5% orless, it follows that (a) and/or the diluent will comprise substantiallyall of the composition.

If one or more diluent polymers are used, those polymers may comprise,in total, as much as 99% by weight of the scavenging component.

Any further additives employed would normally not comprise more than 10%of the scavenging component, with preferable amounts being less than 5%by weight of the scavenging component.

As mentioned above, the oxygen scavenging composition may be used in aflexible or rigid single layer or multilayer article. The layerscomprising the composition may be in several forms. They may be in theform of stock films, including "oriented" or "heat shrinkable" films,which may ultimately be processed as bags, etc. The layers may also bein the form of sheet inserts to be placed in a packaging cavity. Inrigid articles such as beverage containers, thermoformed trays or cups,the layer may be within the container's walls. Even further, the layermay also be in the form of a liner placed with or in the container's lidor cap. The layer may even be coated or laminated onto any one of thearticles mentioned above.

In multilayered articles, the oxygen scavenging layer may be includedwith layers such as, but not necessarily limited to, "oxygen barriers",i.e. layers of material having an oxygen transmission rate equal to orless than 500 cubic centimeters per square meter (cc/m²) per day peratmosphere at room temperature, i.e. about 25° C. Typical oxygenbarriers comprise poly(ethylene vinyl alcohol), polyacrylonitrile,polyvinyl chloride, poly(vinylidene dichloride), polyethyleneterephthalate, silica, and polyamides. Copolymers of certain materialsdescribed above, and metal foil layers, can also be employed.

The additional layers may also include one or more layers which arepermeable to oxygen. In one preferred embodiment, especially forflexible packaging for food, the layers include, in order starting fromthe outside of the package to the innermost layer of the package, (i) anoxygen barrier layer, (ii) a layer comprising the invention, i.e. thescavenging component as defined earlier, and optionally, (iii) an oxygenpermeable layer. Control of the oxygen barrier property of (i) allows ameans to regulate the scavenging life of the package by limiting therate of oxygen entry to the scavenging component (ii), and thus limitingthe rate of consumption of scavenging capacity. Control of the oxygenpermeability of layer (iii) allows a means to set an upper limit on therate of oxygen scavenging for the overall structure independent of thecomposition of the scavenging component (ii). This can serve the purposeof extending the handling lifetime of the films in the presence of airprior to sealing of the package. Furthermore, layer (iii) can provide abarrier to migration of (a), (b), other additives, or by-products ofscavenging into the package interior. Even further, layer (iii) may alsoimprove the heat-sealability, clarity and/or resistance to blocking ofthe multilayer film.

The multilayered articles can be prepared using coextrusion, coatingand/or lamination. In addition to oxygen barrier and oxygen permeablelayers, further layers such as adhesive layers may be adjacent to any ofthe layers listed above. Compositions suitable for adhesive layersinclude those well known in the art, such as anhydride functionalpolyolefins.

To determine the oxygen scavenging capabilities of the invention, therate of oxygen scavenging can be calculated by measuring the timeelapsed before the article depletes a certain amount of oxygen from asealed container. For instance, a film comprising the scavengingcomponent can be placed in an air-tight, sealed container of a certainoxygen containing atmosphere, e.g. air which typically contains 20.6%oxygen by volume. Then, over a period of time, samples of the atmosphereinside the container are removed to determine the percentage of oxygenremaining.

When an active oxygen barrier is required, a useful scavenging rate canbe as low as 0.05 cc oxygen (O₂) per gram of (a) in the scavengingcomponent per day in air at 25° C. and at 1 atmosphere pressure.However, the composition of this invention has the capability of ratesequal to or greater than 0.5 cc oxygen per gram of (a) per day, thusmaking it suitable for scavenging oxygen from within a package, as wellas suitable for active oxygen barrier applications. The composition iseven capable of more preferable rates equal to or greater than 5.0 cc O₂per gram of (a) per day.

Generally, film layers suitable for use as an active oxygen barrier canhave a scavenging rate as low as 1 cc oxygen per square meter per daywhen measured in air at 25° C. and 1 atmosphere pressure. However, alayer of this invention is capable of a scavenging rate greater than 10cc oxygen per square meter per day, and preferably has an oxygenscavenging rate equal to or greater than about 25 cc oxygen per squaremeter per day under the same conditions, thus making it suitable forscavenging oxygen from within a package, as well as suitable for activeoxygen barrier applications. Under different temperature and atmosphericconditions, the scavenging rates of the composition and layers of theinvention will be different. The rates at room temperature and oneatmosphere were measured because they best represent the conditionsunder which the invention will be exposed in many instances.

In an active oxygen barrier application, it is preferable that thecombination of oxygen barriers and any oxygen scavenging activity createan overall oxygen transmission rate of less than about 1.0 cubiccentimeters per square meter per day per atmosphere at 25° C. It is alsopreferable that the oxygen scavenging capacity is such that thistransmission rate is not exceeded for at least two days. See EuropeanApplication 301,719. Another definition of acceptable oxygen scavengingis derived from testing actual packages. In actual use, the scavengingrate requirement will largely depend on the internal atmosphere of thepackage, the contents of the package and the temperature at which it isstored. In actual use, it has been found that the scavenging rate of theoxygen scavenging article or package should be sufficient to establishan internal oxygen level of less than 0.1% in less than about fourweeks. See Mitsubishi literature supra.

In a packaging article according to this invention, the scavenging ratecapability will depend primarily on the amount and nature of (a) and(b), and secondarily on the amount and nature of other additives (e.g.,diluent polymer, antioxidant, etc.) which are present in the scavengingcomponent, as well as the overall manner in which the package isfabricated, e.g., surface area/volume ratio.

The oxygen scavenging capacity of an article comprising the inventioncan be measured by determining the amount of oxygen consumed until thearticle becomes ineffective as a scavenger. The scavenging capacity ofthe package will depend primarily on the amount and nature of (a)present in the scavenging component.

In actual use, the oxygen scavenging capacity requirement of the articlewill largely depend on three parameters of each application:

(1) the quantity of oxygen initially present in the package,

(2) the rate of oxygen entry into the package in the absence of thescavenging property, and

(3) the intended shelf life for the package.

The scavenging capacity of the composition can be as low as 1 cc oxygenper gram, but is preferably at least 10 cc oxygen per gram, and morepreferably at least 50 cc oxygen per gram. When such compositions are ina layer, the layer will preferably have an oxygen capacity of at least250 cc oxygen per square meter per mil thickness and more preferably atleast 1200 cc oxygen per square meter per mil thickness.

Other factors may also affect oxygen scavenging and should be consideredwhen selecting compositions for the scavenging. These factors includebut are not limited to temperature, relative humidity, and theatmospheric environment in the package. See Examples 9-18.

As illustrated in the Examples, some embodiments of the invention gothrough an "induction period" before they exhibit oxygen scavenging. Itis believed that antioxidants present in commercially availablematerials used to make the invention increases the induction period. Forinstance, comparison of Examples 25 and 26; 20 and 28; 21 and 27; and 29and 30 illustrates increased induction periods. To counter theantioxidant and thus decrease its effect, peroxides can be added. Othermethods of countering the antioxidant would include extracting it priorto fabrication. See Example 25. Even further, materials absentantioxidants could be selected to make the invention.

In order to further illustrate the practice of the present invention andthe advantages thereof, the following examples are provided. However,these examples are in no way meant to be limitive, but merelyillustrative.

COMPARISON EXAMPLE

A film of poly(ethylene-vinyl acetate) was prepared and tested asfollows. A solution of 2.0 g ELVAX® poly(ethylene-vinyl acetate) having28% by weight vinyl acetate (EVA-28) from Du Pont was prepared in 20milliliters (mL) tetrahydrofuran (THF) and 5 mL toluene with warming.Sufficient NOURY-DRY® cobalt solution from Akzo Chemicals was added togive a loading of 470 ppm. The resulting formulation was solvent castunder nitrogen onto a surface coated with TEFLON® non-stick coating.Afterwards, the dried film was removed and placed in a 125 mL flaskwhich was stoppered with a rubber septum. Oxygen content in the flaskwas then monitored by removing 4 cc samples with a gastight syringe atvarious time intervals and analyzing the samples using a MOCON® model LC700F oxygen analyzer. The gas samples removed were replaced withnitrogen to maintain atmospheric pressure within the flask. The resultsare summarized below:

    ______________________________________                                                Day  % Oxygen                                                         ______________________________________                                                0    20.6                                                                     3    20.3                                                                     4    20.1                                                                     6    19.7                                                                     10   19.7                                                                     13   19.3                                                             ______________________________________                                    

These results illustrate that no detectable scavenging occurred underthe test method employed. It is believed that the observed slightdecrease in oxygen level is fully attributable to the samplingprocedure, which involves replacement of the sampled air in the flaskwith pure nitrogen.

EXAMPLE 1

A solution of 2.16 g of trans-poly(isoprene) from Aldrich was preparedin 65 mL of tetrahydrofuran, THF, with warming. The THF used containedbetween 1000-2000 ppm of peroxides, as measured with EM QUANT® peroxidetest strips from EM Science, Inc. Sufficient NOURY-DRY® cobalt solutionfrom Akzo Chemicals was added to achieve a loading of 4,400 ppm ofcobalt based on the pure metal. A 3.0 mm thick wet film was then castfrom the resulting solution in a nitrogen atmosphere. The cured film wasplaced in a 125 mL Erlenmeyer flask containing air and was stopperedwith a rubber septum. Oxygen levels of the atmosphere in the flask weremeasured according to the method described in the Comparison Example.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                                0      20.6                                                                   1      20.3                                                                   4      19.8                                                                   7      19.1                                                                  11      0.60                                                                  13      0.25                                                                  15      0.15                                                                  19      0.08                                                           ______________________________________                                    

EXAMPLE 2

A solution of 2.0 g of poly(ethylene-vinyl acetate) (28% vinyl acetate),EVA-28, was prepared with warming in 20 mL of THF containing peroxidesas described in Example 1 and 5 mL of toluene. Squalene from Aldrich wasadded to give 15% by weight (total), and sufficient NOURY-DRY® cobaltsolution was added to give 500 ppm cobalt (as metal). A 1.6 mm thick wetfilm was cast, cured and tested as in Example 1.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                               0       20.6                                                                  1       20.3                                                                  2       19.0                                                                  5       0.32                                                                  6       0.01                                                           ______________________________________                                    

EXAMPLE 3

A film was prepared and tested as in Example 2, except CASTUNG® 103 GHdehydrated castor oil from Caschem was used in place of squalene. Thecastor oil was loaded at 15% by weight and the cobalt catalyst at 500ppm.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                               0       20.5                                                                  1       0.02                                                                  4       0.03                                                                  5       0.02                                                           ______________________________________                                    

EXAMPLE 4

The same materials and methods described in Example 3 were used andrepeated except that a catalyst loading of 400 ppm and a dehydratedcastor oil loading of 25% by weight were used.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                               0       20.6                                                                  1       0.04                                                                  2       0.01                                                                  3       0.00                                                           ______________________________________                                    

EXAMPLES 5-8

For these examples, the following formulations were prepared in aBRABENDER® mixing chamber. Films were prepared by pressing in a CARVER®heated lab press. The films tested were in the range of 2-4 g and were8-15 mils thick. The films were sealed in barrier bags, which wereinflated with 130 cc of air. The bags were inflated by means of a needlethrough an adhesive rubber strip, which also allowed the removal of 4 ccgas samples. No allowance was made for the decrease in volume.

The polymers tested were LOTRYL® 3600 ethylene-butyl acrylate having 30%by weight butyl acrylate and 3610 ethylene-methyl acrylate having 29%methyl acrylate from Sartomer-Atochem Co.; PRIMACOR® 5980ethylene-acrylic acid having 20% acrylic acid from Dow Chemical; and1,2-polybutadiene from Scientific Polymers Products, Inc.. All of thesamples tested contained 15% by weight CASTUNG® 103 GH dehydrated castoroil from Caschem Co. and a cobalt (NOURY-DRY® solution) loading of 500ppm. In the following table, the induction period is the time elapsed indays before the film exhibited oxygen scavenging properties. The time(days) it took for all of the oxygen to be consumed (0,000) and thelength of time (days) over which the film was tested are also recordedbelow.

    ______________________________________                                                                             Days                                     Exam-          Castor         Induction                                                                            to   Days                                ple   Polymer  Oil(a)  Co(II)(b)                                                                            (days) 0.000                                                                              Running                             ______________________________________                                        5     Lotryl   15%     500    1      4    63                                        3600                                                                    6     Lotryl   15%     500    1      8    64                                        3610                                                                    7     Primacor 15%     500    1      c    28                                        5980                                                                    8     1,2-Poly-                                                                              15%     500    3      d    33                                        butadiene                                                               ______________________________________                                         (a)percentage by total weight                                                 (b) in ppm                                                                    c oxygen level at 0.43%                                                       d oxygen level at 2.38%                                                  

EXAMPLES 9-18 Conditions Affecting Oxygen Scavenging

The atmospheric conditions under which the oxygen scavengers were testedwere varied to simulate the packaging of moist and dry products as wellas some modified atmosphere packaging (MAP) conditions. See footnotes band c of the following table. Temperature was varied as well. Thesetests were conducted with 130 cc of the atmospheres specified in thetable below. The examples were prepared according to the methoddescribed for Examples 5-8. The compositions all contained 500 ppmcobalt from NOURY-DRY® solution, and as indicated below, all samplesexcept those in Examples 17-18, contained ethylene-vinyl acetate, i.e.EVA-9 and EVA-28. Examples 17-18 illustrate films containing LOTRYL®3610 ethylene-methyl acrylate and 3600 ethylene-butyl acrylate. Allsamples contained either 15% or 25% by weight CASTUNG® 103 GH dehydratedcastor oil. The induction period, the time elapsed before all of theoxygen was consumed, and the length of time over which the film wastested were also recorded.

    ______________________________________                                                                           Induc-                                                                              Days Days                            Exam-         Castor               tion  to   Run-                            ple   Polymer Oil     Variations                                                                            Gas  (Days)                                                                              0.000                                                                              ning                            ______________________________________                                         9    EVA-9   25%     1 mL H.sub.2 O                                                                        a    1     17   30                              10    EVA-28  15%     1 mL H.sub.2 O                                                                        a    5     25   27                              11    EVA-9   25%     10 gm   a    1     6    28                                                    Dessicant                                               12    EVA-28  15%     10 gm   a    1     11   27                                                    Dessicant                                               13    EVA-9   15%     40% RH  b    1     4    31                              14    EVA-28  25%     42% RH  b    1     8    32                              15    EVA-9   15%     40% RH  c    1     4    30                              16    EVA-28  25%     42% RH  c    3     8    32                              17    Lotryl  15%     Room Temp.                                                                            a    <1    8    65                                    3610                                                                    18    Lotryl  15%     -5° C.                                                                         a    <1    13   65                                    3600.sup.d                                                              ______________________________________                                         a Air, i.e. 20.6% O.sub.2                                                     b 3.1% O.sub.2, Balance N.sub.2                                               c 0.93% O.sub.2, 30.3% CO.sub.2 Balance N.sub.2                               .sup.d Compare with Example 5 which illustrates scavenging by 3600 at roo     temperature.                                                             

From the above results, it does not appear that varied humidity levelssignificantly affect scavenging performance. See Examples 9-12. Further,low oxygen content does not significantly affect scavenging performance.See Examples 13-16. In addition, the presence of carbon dioxide does notaffect that performance. See Examples 15 and 16. Comparison of Examples17 and 18, and Example 5 from the previous table illustrates thatscavenging performance is not significantly affected by lowertemperatures.

EXAMPLES 19-26

Except for Example 26, films illustrated in these Examples were preparedby solvent casting methods described in Examples 1-4 and tested asillustrated in Examples 5-8. Example 19 illustrates that casting a filmusing a solvent such as methylene chloride will produce essentially thesame results seen in melt blended films. Compare with Examples 9-12.

These Examples also provide support for the belief that antioxidantshave an effect on the induction period and that the addition ofperoxides can be used to reduce that effect. Example 24 illustrates theeffect which 2,6-di-t-butyl-4-methylphenol (BHT) has on the inductionperiod. Compare with Example 23. It is believed that Examples 20-22illustrate how peroxides reduce the effect of antioxidants because it isbelieved that the polymers employed in Examples 20-22 containantioxidants typically used with those polymers. Example 25 illustratesthe effect of antioxidant by measuring the induction period of acomposition which has had antioxidant extracted. Compare with Example26.

In Example 21, "c/t" refers to cis/trans.

    ______________________________________                                                                           Induc-                                                                              Days Days                            Exam-          Castor              tion  to   Run-                            ple   Polymer  Oil     Co(II)                                                                              Solvent                                                                             (Days)                                                                              0.000                                                                              ning                            ______________________________________                                        19    EVA-4U   25%      500  CH.sub.2 Cl.sub.2                                                                   2     8    56                              20    trans-   .sup. 15%.sup.b                                                                       1000  THF.sup.c                                                                           14    17   58                                    Poly-                                                                         isoprene.sup.a                                                          21    c/t-1,4-  0%     1000  THF.sup.c                                                                           2     5    32                                    Poly-                                                                         butadiene                                                               22    1,2-Poly-                                                                               0%     1000  THF.sup.c                                                                           1     2    35                                    butadiene                                                               23    EVA-28   20%      500  THF.sup.c                                                                           1     4    73                              24    EVA-40   25%      500  THF.sup.d                                                                           d     d    90                              25    1,2-Poly-                                                                               0%      500  f     <1    10   16                                    butadiene.sup.e                                                         26    1,2-Poly-                                                                               0%      500  h     28    39   46                                    butadiene.sup.g                                                         ______________________________________                                         .sup.a scavenging was not noticed when cispolyisoprene was used; the film     resulting from transpolyisoprene was somewhat brittle and opaque.             .sup.b squalene was used in place of castor oil.                              .sup.c with peroxides (1000-2000 ppm).                                        d with 0.15% BHT antioxidant; has not scavenged.                              .sup.e RB830 1,2polybutadiene from Japan Synthetic Rubber which had           antioxidant extracted by soxhlet extraction with acetone for 48 hours;        this polymer was tested in 390 cc air.                                        f 25 mL methylene chloride and 10 mL toluene.                                 .sup.g 1,2polybutadiene from Scientific Polymer Products, Inc.; believed      to contain antioxidants typically added to such polymers.                     h Example 26 was melt blended and pressed.                               

EXAMPLE 27

The following formulation was prepared in a BRABENDER® mixing chamber:30 g of low density polyethylene from Union Carbide, 10 g ofcis-/trans-1,4-polybutadiene from Scientific Polymer Products, Inc. andsufficient NOURY-DRY® solution to make 500 ppm. The formulation wasmixed for 15 minutes at 130° C. A film weighing 2-4 g was pressed andtested as in Examples 5-8.

    ______________________________________                                               Time (Days)                                                                           Percent Oxygen                                                 ______________________________________                                                0      20.6                                                                   3      20.6                                                                   7      20.6                                                                  10      20.0                                                                  11      17.5                                                                  12      12.7                                                                  17      0.000                                                                 21      0.000                                                                 48      0.000                                                                 70      0.000                                                          ______________________________________                                    

EXAMPLE 28

A film weighing 2-4 g and having the following formulation was preparedand tested as described in Example 27: 35.9 g low density polyethylene,8.9 g trans-polyisoprene, and sufficient NOURY-DRY® solution to have 500ppm cobalt.

    ______________________________________                                               Time (Days)                                                                           Percent Oxygen                                                 ______________________________________                                                0      20.6                                                                   4      20.6                                                                  14      20.4                                                                  21      20.4                                                                  28      18.5                                                                  35      1.66                                                                  39      0.000                                                                 59      0.000                                                          ______________________________________                                    

EXAMPLE 29

To a 50 mL beaker was added 2.06 g of ethylene-vinyl acetate EVA-28 (28%vinyl acetate) and 20 mL of THF containing peroxides. With warming, ahomogeneous solution was obtained. To the solution was added 0.517 ofCASTUNG® 103 GH dehydrated castor oil from Caschem, and a sufficientamount of manganese carboxylate solution from Mooney Chemical to make500 ppm manganese relative to the total weight of the combined solids. Afilm having a 1.6 mm wet thickness was then cast under a nitrogenatmosphere. The cured film was sealed in a barrier bag containing 130 ccof air and the oxygen content thereof was monitored periodically asdescribed in the Examples above.

    ______________________________________                                                Day  % Oxygen                                                         ______________________________________                                                0    20.6                                                                     1    4.9                                                                      2    0.58                                                                     3    0.000                                                                    35   0.000                                                            ______________________________________                                    

EXAMPLE 30

To a 50 mL beaker was added 2.08 g of EVA-40 ethylene-vinyl acetate fromPolysciences Inc. and 25 mL of methylene chloride. With warming ahomogeneous solution was obtained. To the solution was also added 0.096g of CASTUNG® 103 GH castor oil and a sufficient manganese carboxylatesolution from Mooney Chemical to make 500 ppm manganese relative to thetotal weight. A film having a wet thickness of 1.6 mm was then cast asdescribed in Example 29. The cured film was sealed in a barrier bag with130 cc of air, with the oxygen content thereof measured as described inthe above Examples.

    ______________________________________                                                Day  % Oxygen                                                         ______________________________________                                                 0   20.6                                                                      1   20.5                                                                      7   20.0                                                                     13   19.5                                                                     15   7.0                                                                      18   0.000                                                                    31   0.000                                                            ______________________________________                                    

EXAMPLE 31

To a 50 mL beaker was added 2.07 g of 1,2-polybutadiene, which had beensoxhlet extracted as in Example 25, along with 20 mL of methylenechloride and 13 mL of toluene. The mixture was warmed until ahomogeneous solution was obtained. Sufficient manganese carboxylate fromMooney Chemical was added to give 500 ppm Mn (as metal). A 1.6 mm thick(wet) film was then cast under a nitrogen atmosphere. The cured film wasplaced in a barrier bag inflated with 390 cc of air. Headspace oxygenlevel was monitored as described above.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                                0      20.6                                                                   1      20.6                                                                   8      20.6                                                                  12      4.8                                                                   13      2.8                                                                   14      1.12                                                                  16      0.013                                                                 20      0.000                                                                 26      0.000                                                          ______________________________________                                    

EXAMPLE 32

A masterbatch containing cobalt was prepared by a continuous compoundingand a pelletizing operation. Thus, a dry blend of poly(ethylenevinylacetate), vinylacetate 9% (EVA-9), containing 2.3% by weightpellets of TEN-CEM® cobalt (22.5% cobalt by weight) catalyst from MooneyChemicals was placed in the hopper of a BRABENDER® counter-rotating,intermeshing, twin screw extruder, equipped with a strand die. Theextruder was maintained at 120° C., with the die at 110° C. Theresulting strand was fed through a water bath to cool and was dried withan air knife. The strand was then fed into a pelletizer.

EXAMPLE 33

A 2-4 g pressed film of the following formulation was prepared asdescribed in Example 27: 26.0 g low density polyethylene, 10.0 g ofpoly(styrene-butadiene) (23% styrene) from Scientific Polymer Products,and 4 g of the masterbatch prepared according to Example 32. The filmwas tested as described in Examples 5-8, except that 390 cc of air wasused.

    ______________________________________                                               Time (Days)                                                                           % Oxygen                                                       ______________________________________                                                0      20.6                                                                   3      19.7                                                                   4      18.7                                                                   5      16.8                                                                   7      12.3                                                                  11      5.9                                                                   14      3.3                                                                   17      2.11                                                                  19      1.89                                                                  21      1.11                                                                  24      0.79                                                                  27      0.53                                                                  31      0.38                                                           ______________________________________                                    

While the invention has been described with preferred embodiments, it isto be understood that variations and modifications may be resorted to aswill be apparent to those skilled in the art. Such variations andmodification are to be considered within the purview and the scope ofthe claims appended hereto.

What is claimed:
 1. An article for packaging an oxygen-sensitiveproduct, which article in use envelops the product and comprises a layersuitable for scavenging oxygen comprising an oxygen scavenging componentconsisting essentially of(a) an ethylenically unsaturated hydrocarbonpolymer having a molecular weight of at least 1,000 and (b) 10-10,000parts per million based on component (a) of transition metal atom of atransition metal salt; wherein the rate of oxygen scavenging of thelayer at 25° C. and one atmosphere of air is at least 1 cc oxygen persquare meter per day and the scavenging capacity is at least 250 ccoxygen per square meter per mil thickness of the layer, and whereinscavenging occurs during the storage of the product in the package. 2.An article according to claim 1 wherein the layer comprises a mixture ofethylenically unsaturated hydrocarbons (a).
 3. An article according toclaim 1 wherein (a) is derived from squalene.
 4. An article according toclaim 1 wherein (a) is derived from dehydrated castor oil.
 5. An articleaccording to claim 1, wherein said layer is flexible.
 6. An articleaccording to claim 1 wherein said layer is transparent.
 7. An articleaccording to claim 1 wherein (a) is a substituted ethylenicallyunsaturated hydrocarbon.
 8. An article according to claim 7 wherein thesubstituted ethylenically unsaturated hydrocarbon comprises anoxygen-containing moiety.
 9. An article according to claim 8 wherein theoxygen-containing moiety is selected from the group consisting ofesters, carboxylic acids, aldehydes, ethers, ketones, alcohols,peroxides and hydroperoxides.
 10. An article according to claim 1wherein (a) is an unsubstituted ethylenically unsaturated hydrocarbon.11. An article according to claim 10 wherein (a) is selected from thegroup consisting of polybutadiene, polyisoprene, an isoprene copolymerand butadiene copolymers.
 12. An article according to claim 10 wherein(a) is 1,2-polybutadiene.
 13. An article according to claim 1 whereinsaid metal is cobalt.
 14. An article according to claim 13 wherein (b)is selected from the group consisting of cobalt neodecanoate and cobalt2-ethylhexanoate.
 15. An article according to claim 1 wherein said metalis manganese.
 16. An article according to claim 15 wherein (b) is amanganese carboxylate.
 17. An article according to claim 1 wherein saidlayer in addition comprises polymeric diluent.
 18. An article accordingto claim 17 wherein said diluent is a thermoplastic polymer.
 19. Anarticle according to claim 18 wherein said thermoplastic polymer isselected from the group consisting of polyethylene and ethylenecopolymers; polypropylene and propylene copolymers; polystyrene andstyrene copolymers; and a blend of any of the above.
 20. An articleaccording to claim 18 wherein said diluent comprises 1% to 99% by weightof the layer.
 21. An article according to claim 11 wherein said layer isadjacent to one or more additional layers.
 22. An article according toclaim 21 wherein at least one additional layer is an oxygen barrier. 23.An article according to claim 22 wherein said oxygen barrier comprises amaterial selected from the group consisting of poly(ethylene-vinylalcohol), polyacrylonitrile, poly (vinyl chloride), polyamides, poly(vinylidene dichloride), poly (ethylene terephthalate), silica and metalfoil.
 24. An article according to claim 21 wherein one or more of saidadditional layer or layers is coextruded with said layer.
 25. An articleaccording to claim 20 wherein one or more of said additional layer orlayers is laminated onto said layer.
 26. An article according to claim21 wherein one or more of said additional layer or layers is coated ontosaid layer.
 27. An article as in any of the proceeding claims whereinthe article exhibits a transmission rate equal to or less than 1.0 ccoxygen per square meter of article surface per day per atmosphere at 25°C.
 28. An article as in any of the proceeding claims wherein said layerscavanges oxygen at a rate sufficient to reduce the amount of oxygen inan atmosphere within the article to less than 0.1% by volume in lessthan four weeks.